2015湘潭市第七届大学生程序设计竞赛 —— Fraction

题目大意：

　　小数化分数，但是分母限制在[1,1000],很明显的枚举，但是在赛场上的时候傻逼了，无论怎么枚举，怎么二分就是wa，wa到死···········。

（ps：我要给出题人寄刀片~~~~），这个题目需要注意的是有可能输出0/1.

#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
const int maxn = 501000;

struct node
{
    int x, y;
};
node stu[maxn];
bool cmp (node a, node b)
{
    return a.x*1.0/a.y < b.x*1.0/b.y ? true : false;
}

int gcd (int a, int b)
{
    return a%b==0?b:gcd(b, a%b);
}

int Bin_Sreach(double n, int low, int high)
{
    while (low <= high)
    {
        int mid = (low + high) / 2;
        double num = stu[mid].x * 1.0 / stu[mid].y;
        if (num < n)
            low = mid;
        if (num > n)
            high = mid;
        if (high - low == 1)
            break;
    }
    double num1 = stu[low].x*1.0 / stu[low].y;
    double num2 = stu[high].x*1.0 / stu[high].y;
    if (fabs(n - num1) > fabs(n - num2))
        return high;
    return low;
}
int main ()
{
    int t, k = 1;
    
    stu[0].y = 1;
    for (int i=1; i<=1000; i++)
        for (int j=i; j<=1000; j++)
        {
            if (gcd(j, i) == 1)
            {
                stu[k].x = i;
                stu[k++].y = j;
            }
        }
        sort (stu, stu+k, cmp);
        
        scanf ("%d", &t);
        while (t --)
        {
            double n;
            scanf ("%lf", &n);
            int p = Bin_Sreach(n, 0, k-1);
            printf ("%d/%d
", stu[p].x, stu[p].y);
        }
        return 0;
}